Conventional shielded communication cables generally have one or more inner “signal” conductors which are surrounded by an outer conductor known as a “shield.” The signal conductor(s) and the shield conductor are separated by a dielectric medium. This construction ensures efficient transmission of signals via the signal conductor(s) with little or no signal leakage outside the shield conductor. Additionally, this construction greatly reduces external electrical noise from interfering with the signal conductor(s).
Communication subscriber services, for example, cable television, Internet, digital telephone, digital data, etc., may use such conventional shielded communication cables and/or connectors in a variety of applications. For example, at each subscriber location, a shielded cable commonly forms a connection between the subscriber's service point and the provider's communications network. To provide safe and efficient operation, the shield conductor for the shielded cable may be connected to the subscriber's building/facility electrical grounding system at one end and to the communication system provider's network grounding system at the other end. In turn, the communication system provider's network grounding system is generally connected to electrical utility grounding system. Hence, the cable shield assembly of conventional shielded communication cable in a typical communication system forms an electrical connection between the subscriber's building electrical grounding system and the electrical utility grounding system.
Historically, coaxial shields of shielded communication cables do not have overcurrent protection because it is presumed that overcurrent protection is already in place for the associated signal conductors of the shielded communication cables, which also provides such protection for returning currents for the shield conductors.
Electrical utility power in the United States is typically provided with a grounded neutral conductor. The neutral conductor for electrical service to a building is connected to the building electrical grounding system at one end and to the electrical utility's network grounding system at the other end. On a building which is also served by shielded communication subscriber service cable(s), such an arrangement results in an unintended parallel path for electrical utility neutral currents on the communications cable shield. Consequentially, some amount of unintended utility neutral current will always flow on the communications system shield. These shield currents (objectionable currents) are commonly small and usually go unnoticed. However, if discontinuities or poor connections occur in the electrical system neutral conductor, significant objectionable current may then flow on the communications cable shield, easily exceeding what the communications cable shield assembly can safely carry. This results in a significant risk of fire, or damage (e.g., to the network itself or to equipment/wiring inside the subscriber's premises), due to dangerous electrical overheating of the communications cable shield.
The coaxial shield overcurrent, as described above, may be a symptom of another serious problem with the building electrical system, i.e., the discontinuities or poor connections in the electrical system neutral conductor. In such a circumstance, even if the shield overcurrent hazards are somehow remedied, it would not alleviate the underlying problem in the neutral conductor (which also carries serious potential risk of fire or electric shock). Hence, elimination of the overcurrent flow in the shield conductor may resolve one dangerous condition (the risk of fire or damage from overheating in the shield conductors), but it does not eliminate the substantial risk of fire or electrical shock elsewhere that can result from discontinuities or poor connections in the electrical system neutral conductor.
Hence, there is an unresolved need for a circuit, a device, and/or a system for preventing overcurrent currents in shielded coaxial communication cable assemblies and related networks.